Movie vs. Book

Last week I saw My Sister's Keeper. I had been excited to see it since the book was so amazing. I had read it years ago as part of a book club and it was an instant favorite. In fact, I think it is the book that showed how much Jodi Picoult had matured and grown as a writer. Her previous books were very predictable and fluffy (I read her previously-published novels after reading My Sister's Keeper). But with My Sister's Keeper she brought to life a story that was similar to present day headlines and was a story that needed to be imagined. And what a wonderful perspective she imagined it from. I loved the book and have recommended it many times over the years.
Back to the movie- so as the movie starts I immediately feel like something is off. The screen keeps fading to black when a new character is introduced. It feels like the class project of Film Editing 101 when they learn to use the fade button. The black screen with voice over doesn't fit and seems disjointed.
The second thing I notice is that the songs in the movie are really good, mostly, but it almost seems like they are thrown in haphazardly. Like they wrote the scene just so they could throw in a good song.
I will say this, the acting was good, especially by Sofia Vassileva, who was remarkable. Cameron Dias was good, but a little hard to believe her as a mother (and couldn't she wash her hair?).
And lastly, who wrote this screenplay? It barely follows the book! I understand the need to edit for time and to keep the story line simple for a two hour movie. But why do they (movie makers) make up whole new lives for their characters? Why do they make up whole new endings for the movie?? Wasn't the book a national bestseller, don't people LOVE it just the way it is?
Movie makers must think their audience is stupid. We can't possible follow the story from the book, right? It makes me very angry and I am sorry to resort to sarcasm but, but....arrggg!
The last thing I am going to mention on this subject is The Time Traveler's Wife. One of the best books I have ever read, or reread. After years of post-production and years of production it is finally coming out on the big screen. The sad part for me is, from the movie's previews I have seen, it looks like it is barely based on the book. I can't decide if I should go see it or if it will only make my blood boil.
Now there are movies-based-on-books that I have loved almost as much as the book- Pride and Prejudice, Cold Mountain, Jane Eyre, Fight Club, but why do so many fall short?

I would love to read your comments on your favorite book that was made into a movie...